Landing Simulation in the Full Two-Body Problem of Binary Asteroids

This paper investigates the motion of a lander in a fully coupled spin-orbit binary system. The full dynamical equations are established, including the states of the lander and the two small celestial bodies. The binary companions are represented by tetrahedral meshes when propagating their states; therefore, their irregular shapes are preserved. The mutual gravitational interactions between the two bodies and the attraction of the lander in this binary system are evaluated by the finite element method. The contact motion between the lander in arbitrary shapes/inertia and the asteroid surface is processed by the polygonal contact model. The resulting framework is applied to the binary asteroid system, 66391 Moshup. The deployment simulations of four typical initial positions near the secondary body suggest the lander release should avoid polar regions. The dynamical effect of the primary body on the lander is also investigated. The numerical results show that the accumulative effect of the weak tidal force from the primary body is nonnegligible. In addition, four different internal structures of the secondary body are constructed by operating the tetrahedron mesh. The touchdown positions and settling time of the landing trajectories on these four models are summarized and compared. The results indicate that variations of the internal structure have a nonnegligible effect on the local gravitational field around the secondary body, and therefore affect the locomotion of the lander.